Cabinet for numerical controller

ABSTRACT

A casing structure for a numerical control unit in which a cooling fan mounted on a fan cover is electrically connected with a control board attached to a main cover without using cables. A terminal unit connected with wiring of a fan motor is fixed to a fan cover, and a power supply terminal to be directly connected with the terminal unit is fixed to an upper end portion of a main control board The terminal unit is connected with or disconnected from the power supply terminal by attaching or detaching the fan cover to or from a casing body. Since cables are not needed for connection, a casing can be assembled and disassembled easily. Further, since an assembling error due to interference of cables is eliminated, automation of the assembling work can be easily achieved.

DESCRIPTION

1. Field of the Invention

The present invention relates to an improvement of a casing structurefor a numerical control unit.

2. Description of the Related Art

There is already known a casing structure for a numerical control unitcomprising a casing body, a main cover and a sub-cover for closing afront opening of the casing body, and a fan cover attached to a top ofthe casing body.

Generally, in this kind of casing structure, a cooling fan is mounted onthe fan cover, which is to be attached to the top of the casing body, tothereby form a unit, and installation of the cooling fan to the casingbody is performed simultaneously with attachment of the fan cover to thecasing body. However, it is necessary to connect wiring of the coolingfan to a power supply terminal on a control board attached to the maincover, with cables. Thus, if the casing is to be assembled by hand, acumbersome work is needed in arranging the cables, and if the casing isto be assembled by an automated operation, an assembling error mayhappen due to interference of the cables.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a casing structure fora numerical control unit in which a cooling fan mounted on a fan coveris electrically connected with a control board attached to a main coverwithout using cables.

A casing structure for a numerical control unit of the present inventioncomprises: a casing body, a front cover for closing a front opening ofthe casing body, a fan cover attached to a top of the casing body, acontrol board attached to the front cover, a guide rail provided insidethe casing for inserting and fixing the control board, locking membershaving release mechanisms provided at fitting portions of the covers andthe casing body, a connection board provided on a rear side of thecasing body and connected with a terminal on the control board, acooling fan mounted on the fan cover, a terminal fixed to the fan coverand connected with wiring of the cooling fan, and a power supplyterminal fixed to an upper end portion of the control board attachedupright to the front cover, to be directly connected with the terminalfixed to the fan cover.

The casing structure for a numerical control unit of the presentinvention may further comprise: a lock mechanism provided between thefan cover and the control board attached to the front cover or betweenthe fan cover and the front cover, to allow the front cover and thecontrol board to be attached or detached only when the fan cover isdetached. With this structure, the terminal fixed to the fan cover andthe power supply terminal on the control board attached to the maincover is prevented from being damaged while the casing is assembled byhand or while the casing is disassembled and assembled for maintenance.

The front cover may be formed of synthetic resin, and a stay forattaching and detaching the control board may be formed integrally withthe front cover. The stay has a support portion for supporting bothsides of the control board and the support portion has a resilienttongue with a dowel at an end thereof to be fitted in a hole provided inthe control board.

The front cover may comprise a main cover and a sub-cover. In this case,the power supply terminal to be connected with the terminal on the fancover is fixed to the control board attached to the main cover, and thelock mechanism is provided between the fan cover and the control boardattached to the main cover or between the fan cover and the main cover.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a left side view showing an embodiment of a casing for anumerical control unit according to the present invention in asee-through manner;

FIG. 2 is a front view showing a main part of the casing of FIG. 1 in asee-through manner;

FIG. 3 is a rear view showing a main part of the casing of FIG. 1 in asee-through manner;

FIG. 4 is a plan view showing a main part of the casing of FIG. 1 in asee-through manner;

FIGS. 5a to 5c show how a sub-cover and a sub-control board areattached, of which FIG. 5b is a front view of the sub-cover and thesub-control board, FIG. 5c a side view thereof, and FIG. 5a an enlargedcross-sectional view parallel to a plan view, showing how a lockingmember provided at the sub-cover is fitted into a casing body; and

FIGS. 6a and 6b show how a main control board is attached to a maincover, of which FIG. 6b is an enlarged view of a stay provided at themain cover and the main control board, and FIG. 6a a cross-sectionalview parallel to a plan view of FIG. 6a.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIGS. 1 to 4, a main part of a casing 1 comprises a bottomportion 2a, a top portion 2b, a rear portion 2c, a left side portion 2d,a right side portion 2f and a front portion 2e, and is comprised of acasing body 2 of synthetic resin, a front cover consisting of a maincover 3 and sub-covers 4, 5 for closing a front opening of the casingbody 2, and a fan cover 6 to be attached to the top of the casing body2.

On the rear face of the main cover 3, at upper and lower end portionsthereof, stays 7, 8 for use in attaching a main control board areprovided to the right as viewed from the front, as shown in FIGS. 1 and2. A main control board 9 which is a rectangular shape and approximatelythe same size as the cross-section of the casing body 2 parallel to theside face thereof is set up on the rear face of the main cover 3 in amanner that it is fixed by the stays 7, 8 at its upper and lower ends.

The stay 8 is formed of synthetic resin integrally with the main cover3, and comprises, as shown in FIGS. 6a and 6b, support portions 8a, 8bfor supporting the main control board 9 on both sides thereof, and asupport portion 8c for supporting the lower end of the main controlboard 9. In the central portion of the support portion 8b, a tongue 8dis formed by making a slit of a horseshoe shape. At the tip of thetongue 8d, on the inside face thereof, a dowel 8e having a tapered faceat its tip is formed to project. The dowel 8e projects into a hole 10bored in the main control board 9 and thereby prevents the main controlboard 9 from falling off the stay 8.

The main control board 9 is attached to the main cover 3 only by pushingthe main control board 9 into the stay 8 in a manner that the corner ofthe main control board 9 is guided by the inside faces of the supportportions 8a, 8b, 8c of the stay 8. Due to wedge effect of the taperedface of the dowel 8e which slides on the edge of the board 9, the dowel8e is automatically raised along the face of the board 9 to therebyrecede from the way of the board 9. When the board 9 is completelyinserted in the stay 8, the dowel 8e returns resiliently and projectsinto the hole 10, so that the board 9 is locked in the stay 8.

The other stay 7 having the formation similar to that of the stay 8 isprovided at the upper end portion of the rear face of the main cover 3to be opposite to the stay 8.

A projection 11 shown in FIG. 6a is a rib adapted to hold the side endportion of the main control board 9 to thereby prevent a warp of theboard 9. A number of such projections are provided on the rear face ofthe main cover 3 along the side end portion of the main control board 9at appropriate intervals.

Since the main cover 3 is integrally molded of synthetic resin,including the stays 7, 8, projections 11, and the like, the productioncost is low. Further, since the stays 7, 8 can fix the main controlboard 9 by virtue of the tongues which are formed integrally with thestays 7, 8, fixing means such as screws, rivets or the like are notneeded. Further, since the main control board 9 can be fixed very easilyonly by pushing the main control board 9 in, assembling can be carriedout easily by hand. Furthermore, it is also easy to automate assemblingwork using machines, since the assembling is completed only by simplypushing the control board in, without using screws, rivets or the like.

At the side end portion of the main control board 9 are fixed variousconnectors 12, 13, 14 for use in connection of parallel cables, inconnection to a servo amplifier and the like, an LED 15 for displayingnumerical information, a push switch 16 and the like. Openings forallowing access to the connectors 12, 13, 14 and the push switch 16 andfor allowing visual observation of the LED 15 are bored in the maincover 3 at the corresponding positions.

At the upper end portion of the main control board 9, a cutout 25 isprovided in accordance with the shape of a tip of a terminal unit 24fixed to the fan cover 6, and facing the cutout 25, a power supplyterminal 23 is fixed to the board 9. At the tip of the terminal unit 24is provided a terminal 24a which is connected with wiring of fan motors22 (having a cooling fan) fixed to the fan cover 6. When the fan cover 6is closed, the terminal 24a fixed to the fan cover 6 is brought inelectrical contact with the power supply terminal 23 fixed to the maincontrol board 9, so that driving power is supplied from the main controlboard 9 to the fan motors 22.

At the upper end portion of the main control board 9, at a positionclose to the main cover 3 is provided a cutout 27 which is part of alock mechanism. When the fan cover 6 is closed, a tip projection 26a ofa rib 26 extending downward from the fan cover 6 projects into thecutout 27.

At a position slightly lower than the cutout 27 is provided a connector66, and an opening for access to an insertion opening 67 of theconnector 66 is bored in the main cover 3. In addition to the above,small boards 68, 69, 70 are overlaid on this side of the main controlboard 9 as viewed in FIG. 1 and fixed to the main control board 9 usingspacers, screws and nuts.

On the front face of the main cover 3, a handle 19 for use in detachingthe main cover 3 is integrally formed at the upper end portion thereof,and a locking member 20 which serves also as a handle is integrallyformed at the lower end portion thereof.

The locking member 20 is formed in a manner that it projects from thelower end portion of the main cover 3, like a letter "V". One leg 20a ofthe locking member is integrally connected with the main cover 3. Theother leg 20b thereof extends through a hole 28 bored in the main cover3 beyond the rear face of the cover 3, and a tapered projection 20cformed at the tip of the leg 20b is fitted in a stepped portion 29formed at the bottom portion 2a of the casing body 2 to thereby preventthe main cover 3 from falling off. In order to release the projection20c from the stepped portion 29, it is only necessary to hold and pressthe legs 20a, 20b of the locking member 20 in the vertical direction tothereby deform the locking member resiliently in a manner that the leg20b is drawn up to the leg 20a to thereby disengage the projection 20cfrom the stepped portion 29 (a quick release mechanism).

At the lower end portion of the main control board 9 are fixedconnectors 17 for use in connection of RS232C cables or the like. In thebottom portion 2a of the casing body 2, openings for letting in cableconnectors 33 to be connected with the connectors 17 are bored at thepositions corresponding to the connectors 17. As shown in FIGS. 2 and 3,a hook hole 18 is bored in the upper end portion of the rear wall of thecasing body 2, and actually, the connectors 17 can be used only when thecasing is used in a manner that it is suspended using the hook hole 18.In the lower end portion of the rear wall of the casing body 2, a hole21 is bored so that a nail, a screw, a bolt or the like planted in awall may be let though the hole 21 to prevent the suspended casing 1from tilting accidentally.

On the inside faces of the bottom and top portions 2a, 2b of the casingbody 2, guide rails 31, 30 having grooves in which the lower and upperend portions of the main control board 9 are to be fitted are formedintegrally. Thus, the main control board 9 can be inserted from thefront opening of the casing body 2 along the guide rails 31, 30.

Further, on the inside face of the rear portion 2c of the casing 2, aprojection 32 having a C-like cross section is formed integrally. Theprojection 32 is adapted to hold the side end portion of the maincontrol board 9 on both sides when the main control board 9 has beencompletely pushed in, to thereby prevent a warp of the main controlboard 9.

The guide rail 30 formed at the top portion 2b is partially cut off atthe positions corresponding to the cutouts 25, 27 of the main controlboard 9 to form vertical through-holes which allow the terminal unit 24and the tip projection 26a of the rib 26 provided at the fan cover 6 toproject therein. The guide rail 31 formed at the bottom portion 2a ispartially cut off at the positions corresponding to the connectors 17 toform vertical through-holes which allow the cable connectors 33 toproject therein. At the top portion 2b of the casing body 2, ducts 34adapted to face the fan motors 22 are formed integrally with the casingbody 2 to lead outside air fed by the fan motors 22 into the casing body2.

FIGS. 5a to 5c show details of a sub-cover 5 and a sub-control board 35.The sub-control board is a function expanding card used for improvingthe function of the numerical control unit, adding an additionalfunction or the like.

On the rear face of the sub-cover 5, stays 36, 37 for use in attachingthe sub-control board are provided at the upper and lower end portionsthereof, and the sub-control board 35 of a rectangular shape is set upon the rear face of the sub-cover 5 in a manner that it is fixed by thestays 36, 37 at its upper and lower ends.

The stay 37 is formed of synthetic resin integrally with the sub-cover5, and comprises, as shown in FIGS. 5b and 5c, support portions 37a, 37bfor supporting the sub-control board 35 on both sides thereof, and asupport portion 37c for supporting the lower end of the sub-controlboard 35. At the tip portion of the support portion 37c, a dowel 37dhaving a tip rounded to be a quadratic surface is formed to project. Thedowel 37d projects into a cutout 38 formed in the sub-control board 35and thereby prevents the sub-control board 35 from falling off.

The other stay 36 has a formation basically similar to that of the stay37, except that the tip of a dowel 36d is not rounded. This is toprevent the cutout 38 from disengaging from the dowel 36d due to aclockwise angular moment as viewed in FIG. 5c which acts on the sub5control board 35 when the sub-cover 5 is detached from the casing 1 andheld by itself.

Thus, in order to attach the sub-control board 35 to the sub-cover 5,first the dowel 36d of the stay 36 is fitted in the cutout 38 on theupper side of the sub-control board 35, and then the lower end corner ofthe board 35 is pushed in in a manner that it is guided by the insidefaces of the support portions 37a, 37b and the dowel 37d of the stay 37.Since the lower end corner of the board 35 comprises a rounded portion39, when the lower end portion of the board 35 is only pushed in thestay 37, the rounded portion 39 of the board 35 slides on the roundedportion of the dowel 37d, and the rounded portion 39 of the board 35 andthe rounded portion of the dowel 37d push each other. As a result, thestay 37 is resiliently deformed easily, and the dowel 37d is fitted andlocked in the cutout 38.

A projection 40 shown in FIG. 5b is a rib for holding the side endportion of the sub-control board 35 to thereby prevent a warp of theboard 35. The projection 40 is provided at an intermediate positionbetween the stays 36, 37 along the side end portion of the sub-controlboard 9.

Since the sub-cover 5 is integrally molded of synthetic resin, includingthe stays 36, 37, the projection 40, and the like, the production costis low. Further, since the stays 36, 37 can fix the sub-control board 35by virtue of the dowels which are formed integrally with the stays 36,37, fixing means such as screws, rivets or the like are not needed.Further, since the sub-control board 35 can be fixed very easily only bypushing the sub-control board 35 in, assembling can be carried outeasily by hand. Furthermore, it is also easy to automate assembling workusing machines, since the assembling is completed only by simply pushingthe sub-control board in, without using screws, rivets or the like.

At the side end portion of the sub-control board 35 is fixed a connector41, and a cutout 42 for allowing access to the connector 41 is formed inthe sub-cover 5 at the corresponding position. A recess 43 of ahood-like shape is a clearance for allowing fingertips to approach andhandle a knob 45 (FIG. 2) provided for unlocking an optical cableconnector 44 (FIGS. 1 and 2) fixed on the main cover 3.

On the front face of the sub-cover 5, a handle 46 for use in detachingthe sub-cover 5 is integrally formed at the lower end portion thereof,and a locking member 47 which serves also as a handle is integrallyformed at the upper end portion thereof.

The locking member 47 has a formation similar to that of the lockingmember 20 of the main cover 3. A tapered projection 47c formed at thetip of a leg 47 is fitted in a slit 48 formed in the left side portion2d of the casing body 2 to thereby prevent the sub-cover 5 from fallingoff. In order to release the projection 47c from the slit 48, it is onlynecessary to hold and press legs 47a, 47b of the locking member 47 inthe horizontal direction to thereby deform the locking member 47resiliently in a manner that the leg 47b is drawn up to the leg 47a tothereby disengage the projection 47c from the slit 48 (a quick releasemechanism).

Since the sub-cover 4 has a formation similar to that of the sub-cover5, the explanation thereof will be omitted. Generally, the sub-controlboard 35 to be attached to the sub-cover 5 and the sub-control board 49to be attached to the sub-cover 4 have functions different from eachother.

On the inside face of the left side portion 2d of the casing body 2, aguide rail 50 having a groove in which the lower end portion of thesub-control board 35 is to be fitted, a guide rail 51 having upper andlower grooves in which the lower end portion of the sub-control board 49and the upper end portion of the sub-control board 35 are to be fitted,respectively, and a guide rail 52 having a groove in which the upper endportion of the sub-control board 49 is to be fitted are formedintegrally with the casing body 2. Thus, the sub-control board 35 andthe sub-control board 49 are inserted from the front opening of thecasing body 2 along the guide rails 50, 51 and the guide rails 51, 52,respectively.

As shown in FIG. 3, in a rear opening which occupies about two thirds ofthe rear portion 2c of the casing body 2 on the lower side is fixed adistribution board 53 for use in wiring for connecting terminals of themain control board 9 or each sub-control board 35, 49 to an externaldevice, connecting the main control board 9 and each sub-control board35, 49 with each other, or connecting the sub-control boards 35, 49 witheach other.

As shown in FIG. 3, an intermediate connector 58 for connection with theterminal 54 (shown in FIGS. 1 and 5c) of the sub-control board 35, anintermediate connector 59 for connection with the terminal 56 (shown inFIG. 1) of the sub-control board 49, and an intermediate connector 60for connection with the terminal 55 (shown in FIG. 1) of the maincontrol board 9 are fixed on the distribution board 53, and theterminals 54, 56, 55 of the control boards can be automaticallyconnected with the intermediate connectors 58, 59, 60 of thedistribution board 53 only by inserting the sub-control boards 35, 49and the main control board 9 into the casing body 2 to which thedistribution board 53 has been fixed.

Such way of connection is already known. Generally, each of theterminals 54, 56, 55 of the control boards is made of printed wiring orthe like formed on each control board, and each of the intermediateconnectors 58, 59, 60 of the distribution board 53 is made of a group ofterminals such as a row of pressed metal terminals of a V-like shapeadapted to nip the printed wiring.

The connectors 17, 17 provided at the lower end portion of the maincontrol board 9 are for use in external connection. Reference numeral 61denotes a test connector accessible from the side of the casing body.

As shown in FIGS. 1 and 3, at the opening portion of the rear portion 2cof the casing body 2 of synthetic resin are provided, integrally withthe casing body 2, ribs 62 for supporting the distribution board 53 onits peripheral and rear sides, and at the lower end portion of the rearportion 2c are provided, integrally with the casing body 2, projections64 for supporting the lower end portion of the distribution board 53 onits front side. In order to attach the distribution board 53 to the rearportion 2c of the casing body 2, first the distribution board 53 istilted and set on the projections 64 with its front face of its lowerend portion leaning on the inside slant faces 64a of the projections 64.Then, the distribution board 53 is swung clockwise as viewed in FIG. 1in a manner that the distribution board 53 is guided by the ribs 62 onboth sides thereof. Finally, the distribution board 53 is locked by thelocking members 65, 63 integrally formed at the rear portion 2c of thecasing body 2 in a manner that the end portions of the distributionboard 53 are fitted behind tapered projections 65a, 63a of the lockingmembers 65, 63 from the front side.

Since the projections 65a, 63a of the locking members 65, 63 aretapered, when the distribution board 53 is only swung and pushed to therear portion 2c of the casing body 2, the end portions of thedistribution board 53 slide on the tapered faces of the projections, andthe end portions of the distribution board 53 and the tapered faces ofthe projections push each other. As a result, the locking members 65, 63are resiliently deformed easily, and the distribution board 53 is fittedbehind the rising portions of the projections 65, 63 and locked thereby.

In order to detach the distribution board 53 from the casing body 2, itis only necessary to raise up the projections 65a, 63a of the lockingmembers 65, 63 by fingers against their resilience to thereby releasethe end portions of the distribution board 53 from the projections 65a,63a, and then to swing the distribution board 53 counterclockwise asviewed in FIG. 1 and to pull it out upward (a quick release mechanism).

Projections 78 planted in the rear portion 2c of the casing body 2 likespikes are positioning projections. The projections 78 are fitted inholes bored in the distribution board 53 at the corresponding positionsso that the distribution board 53 can be positioned accurately relativeto the rear portion 2c of the casing body 1. The lower projection 78 hasa smaller height than the upper projection 78 for fear that it may be ahindrance when the lower end portion of the distribution board 53 is seton the inside slant face 64a of the projection 64 in order to attach thedistribution board 53 or when the distribution board 53 is pulled outand detached.

As shown in FIG. 4, in the top portion 6a of the fan cover 6 are bored aplurality of holes 71 for taking outside air in by fan motors 22. Atboth side end portions of the rear portion 2c of the fan cover 6 areintegrally formed dowels 72 for use in attaching the fan cover 6 to thecasing body 2. As shown in FIGS. 1 and 3, the dowels 72 are fitted inholes 73 of a rectangular shape bored in the rear portion 2c of thecasing body 2.

At the end portion of the fan cover 6 located on the main cover 3 sideis integrally formed a front hanging portion 74 arranged such that thetip portion thereof slightly overlaps the upper end portion of the maincover 3 on the front side when the fan cover 6 is closed. As shown inFIGS. 2 and 4, a cutout 75 is formed in the central portion of the fronthanging portion 74.

At the top portion 6a of the fan cover 6 is integrally formed a lockingmember 76 of a U-like shape having a tapered projection 76a and a tippush portion 76b. As shown in FIGS. 1 and 4, the tip push portion 76bslightly projects forward from the cutout 75 of the front hangingportion 74. The projection 76a of the locking member 76 is, when the fancover 6 is closed, fitted in a slit 77 made in the front portion 2e ofthe casing body 2 to thereby lock the fan cover 6. The front portion 2eof the casing body 2 located above the front opening of the casing body2 is a horizontal strip-like portion rising upward from the top portion2b of the casing body 2 or connecting with the left and right sideportions 2d, 2f of the casing body 2.

In order to attach the fan cover 6, first the fan cover 6 is tilted asindicated by two-dot chain lines in FIG. 1, then the dowels 72 of thefan cover 6 are fitted in the holes 73 of the rear portion 2c, and then,in that state, the fan cover 6 is pushed downward and closed.

When the fan cover 6 is being closed, the projection 76a of the lockingmember 76 and the front hanging portion 74 of the fan cover 6 interferewith the upper edge of the front portion 2e of the casing body 2.However, since those portions are rounded, the projection 76a slides onthe front portion 2e of the casing body, and the projection 76a and thefront portion 2e push each other. As a result, the locking member 76 isresiliently deformed, and does not interfere with the front portion 2eany longer. When the fan cover 6 has been completely closed, the lockingmember 76 returns resiliently and the projection 76a comes into the slit77 of the front portion 2e of the casing body 2. Thus, the fan cover 6is locked in a manner that the rising portion of the projection 76a isfitted in the slit 77.

At that time, the tip of the terminal unit 24 of the fan cover 6 comesinto the cutout 25 of the main control board 9 in a manner that it isguided by a reduced diameter portion of the cutout 25. Thus, theterminal 24a of the terminal unit 24 is connected with the power supplyterminal 23 of the main control board 9, accurately. The tip projection26a of the rib 26 of the fan cover 6 is fitted in the cutout 27 of themain control board 9, to thereby prevent the main control board 9 frombeing pulled out when the fan cover 6 is closed. Further, when the fancover 6 is closed, the lower end portion of the front hanging portion 74of the fan cover 6 covers the outside face of the upper end portion ofthe main cover 3. In addition to the tip end projection 26a fitted inthe cutout 27, this also serves to prevent the main cover 3 from beingdetached, and therefore prevents the main control board 9 from beingpulled out.

In order to detach the fan cover 6, it is only necessary to deform thelocking member 76 resiliently by pushing the tip push portion 76b of thelocking member 76 inward from the front side, to thereby release theprojection 76a from the slit 77, and then to swing the fan cover 6counterclockwise about the dowels 72 as viewed in FIG. 1, and then topull the dowels 72 simply out of the holes 73 of the rear portion 2c (aquick release mechanism).

Next, how the entire casing 1 is assembled or disassembled for purposesof forwarding or maintenance.

First, the main cover 3 and the sub-covers 4, 5 to which the maincontrol board 9 and the sub-control boards 49, 35 are attached,respectively, the fan cover 6 to which the fan motor 22 and the terminalunit 24 are attached, the distribution board 53 and the casing body 2are prepared. Then, the distribution board 53, the main cover 3 and thesub-covers 4, 5, and the fan cover 6 are attached to the casing body 2basically in this order to thereby assemble the casing 1.

The order can be somewhat changed, but it is necessary to make sure thatthe fan cover 6 is attached after the main cover 3 (main control board9) has been attached. Since the terminal unit 24 fixed to the fan cover6 is connected with the power supply terminal 2 fixed to the maincontrol board 9 in a manner that an upper convex portion is fitted in alower concave portion, if it is intended to insert the main controlboard 9 in the guide rails 31, 30 after the fan cover 6 has beenattached to the casing body 2, the terminal unit 24 interferes with themain control board 9 and damage is caused.

In the present embodiment, when the fan cover 6 is attached to thecasing body 6, the tip projection 26a of the rib 26 of the fan cover 6projects through the guide rail 30 downward. Therefore, even if it isintended to insert the main control board 9 in the guide rails 31, 30after the cover 6 has been attached to the casing body 2, the way of themain control board 9 is blocked by the tip projection 26a of the rib 26which is located before the terminal unit 24. Therefore, the maincontrol board 9 can not be inserted further, and the interference of theterminal unit 24 with the main control board 9 is prevented.

At that time, the left upper end portion of the main control board 9 asviewed in FIG. 1 collides with the tip projection 26a of the rib 26.However, since there are no electrical parts arranged at the left upperend portion of the main control board 9, damage is not caused to themain control board 9. The terminal unit 24 is also safe as it isprotected by the tip projection 26a of the rib 26.

Thus, an error in assembling the casing by hand is prevented bypreventing wrong procedure such that the main control board 9 isattached after the fan cover 6 is attached.

Further, the terminal unit 24 and the power supply terminal 23 throughwhich the fan motor 22 and the main control board 9 are connected can beeasily connected only by closing the fan cover 6 after the main controlboard 9 has been attached. Cables do not need to be arranged. Therefore,even if assembling is automated, defective assembling due to theinterference of cables or the like cannot happen.

As already mentioned, the main control board 9 and the sub-controlboards 49, 35 can be easily attached to the main cover 3 and thesub-covers 4, 5 only by pushing the boards 9, 49, 35 in thecorresponding stays 7 and 8, 36, 37, respectively. Further, the maincontrol board 9 and the sub-control boards 49, 35 can be easilyelectrically connected with the distribution board 53 attached to thecasing body 2 only by inserting the boards 9, 49, 35 into the casingbody 2. Further, only by simply pushing the covers 3, 4, 5, 6 in, thelocking members 20, 47, 76 of the covers 3, 4, 5, 6 are fitted in thecasing body 2, and the covers are thereby locked automatically. Thus,the assembling can be carried out with high efficiency, and it is alsopossible to automate the whole assembling procedure using machines.

In order to disassemble the casing 1, the fan cover 6, the sub-covers 4,5, the main cover 3 and the distribution board 53 are detached from thecasing body 2 basically in this order.

The order can be somewhat changed, but it is necessary to make sure thatthe main cover 3 (main control board 9) is detached after the fan cover6 has been detached. This is to prevent the terminal unit 24 fixed tothe fan cover 6 or the power supply terminal 2 fixed to the main controlboard 9 from being damaged as mentioned in respect of assembling.

In the present embodiment, when the assembling is completed and the fancover 6 is closed, the tip projection 26a of the rib 26 of the fan cover6 projects through the cutout 27 and thereby locks the main controlboard 9. In addition, the front hanging portion 74 of the fan cover 6covers the upper end portion of the main cover 3 on the front side andthereby prevents the main cover 3 from being detached. In other words,the present embodiment is so arranged that in the process ofdisassembling the casing 1, the main control board 9 cannot be detachedonly after the fan cover is detached. Thus, the terminal unit 24 and thepower supply terminal 23 are prevented from being damaged.

Further, the fan cover 6, the main cover 3, the sub-covers 4, 5 and thedistribution board 53 can be easily detached in a manner that they arepulled out by handling the locking members 76, 20, 47, 63, 65 havingquick release mechanisms. Therefore, disassembling for maintenance takesonly a very short time.

According to the casing structure of the present invention, the terminalfor the cooling fan fixed to the fan cover is directly connected withthe power supply terminal provided on the control board attached to themain cover in order to drive the cooling fan. Therefore, cables forconnecting the cooling fan and the power supply terminal on the controlboard are not needed any longer, and therefore, arrangement of suchcables does not need to be considered, either. Thus, the fan cover canbe attached or detached easily. Further, since there is no fear thatcables may interfere with each other or become tangled with each otherand cause defective assembling, the assembling can be easily automatedwith machines.

Further, between the fan cover and the control board attached to themain cover and between the fan cover and the main cover are providedlock mechanisms which allow the main cover and the control board to beattached or detached only when the fan cover has been detached. Thisprevents an error such that the control board is pushed in or pulled outwith the fan cover being attached, and thereby prevents the terminal forthe cooling fan or the power supply terminal from being damaged.

Further, each control board can be attached to the casing body by simpleinsertion using guide rails, and the covers on which the control boardsare set up can also easily be attached to or detached from the casingbody by the locking members having quick release mechanisms. Therefore,in the process of maintenance, assembling and disassembling can becarried out quickly and easily. It is also possible to automate thewhole assembling.

What is claimed is:
 1. A casing structure for a numerical control unit,comprising:a casing body; a fan cover to be attached to a top of saidcasing body; a control board accommodated in said casing body; a coolingfan mounted on said fan cover; a terminal fixed to said fan cover andconnected with wiring of said cooling fan; and a power supply terminalfixed to an upper end portion of said control board, to be directlyconnected with said terminal fixed to said fan cover.
 2. A casingstructure for a numerical control unit, comprising:a casing body; afront cover to close a front opening of said casing body; a fan cover tobe attached to a top of said casing body; a control board detachablyattached to said front cover; a guide rail provided inside said casingto guide said control board during insertion and to fix said controlboard; locking members having release mechanisms provided at fittingportions of said covers and said casing body to releasably lock thecovers; a cooling fan mounted on said fan cover; a terminal fixed tosaid fan cover and connected with wiring of said cooling fan; and apower supply terminal fixed to an upper end portion of said controlboard attached to said front cover, to be directly connected with saidterminal fixed to said fan cover.
 3. A casing structure for a numericalcontrol unit according to claim 2, further comprising a lock mechanismprovided between said fan cover and said control board attached to saidfront cover or between said fan cover and said front cover, to allowsaid main cover and said control board to be attached or detached onlywhen said fan cover is detached.
 4. A casing structure for a numericalcontrol unit according to claim 2, wherein said front cover is formed ofsynthetic resin and a stay to attach and detach said control board isformed integrally with said front cover, said stay having a supportportion to support both sides of said control board, and said supportportion having a resilient tongue with a dowel at an end thereof to befitted in a hole provided in said control board.
 5. A casing structurefor a numerical control unit according to claim 2, wherein said frontcover comprises a main cover and a sub-cover, and said power supplyterminal to be connected with said terminal on said fan cover is fixedto said control board attached to said main cover.
 6. A casing structurefor a numerical control unit according to claim 5, wherein said frontcover and said sub-cover are formed of synthetic resin and stays toattach and detach said control board and respectively formed integrallywith said front cover and said sub-cover, each of said stays having asupport portion to support both sides of said control board, and saidsupport portion having a resilient tongue with a dowel at an end thereofto be fitted in a hole provided in said control board.
 7. A casingstructure for a numerical control unit according to claim 2, whereinsaid front cover comprises a main cover and a sub-cover, and said casingstructure further comprises a lock mechanism provided between said fancover and said control board attached to said main cover or between saidfan cover and said main cover, to allow said main cover and said controlboard to be attached or detached only when said fan cover is detached.8. A casing structure for a numerical control unit as recited in claim2, further comprising a connection board provided on a rear side of saidcasing body and connected with a terminal on said control board.
 9. Acasing structure for a numerical control unit, comprising:a casing body;a front cover to close a front opening of said casing body; a fan coverto be attached to a top of said front cover; a control board detachablyattached to said front cover; a guide rail provided inside said casingto guide said control board during insertion and to fix said controlboard; locking members having release mechanisms provided at fittingportions of said covers and said casing body; a connection boardprovided on a rear side of said casing body and connected with aterminal on said control board; a cooling fan mounted on said fan cover;a terminal fixed to said fan cover and connected with wiring of saidcooling fan; a power supply terminal fixed to an upper end portion ofsaid control board attached to said front cover, to be directlyconnected with said terminal fixed to said fan cover; and a lockmechanism provided between said fan cover and said control boardattached to said front cover or between said fan cover and said frontcover, to allow said main cover and said control board to be attached ordetached only when said fan cover is detached.
 10. A casing structurefor a numerical control unit, comprising:a casing body; a front cover toclose a front opening of said casing body; a fan cover to be attached toa top of said front cover; a control board detachably attached to saidfront cover; a guide rail provided inside said casing to guide saidcontrol board during insertion and to fix said control board; lockingmembers having release mechanisms provided at fitting portions of saidcovers and said casing body; a connection board provided on a rear sideof said casing body and connected with a terminal on said control board;a cooling fan mounted on said fan cover; a terminal fixed to said fancover and connected with wiring of said cooling fan; a power supplyterminal fixed to an upper end portion of said control board attached tosaid front cover, to be directly connected with said terminal fixed tosaid fan cover; and wherein said front cover is formed of syntheticresin and a stay to attach and detach said control board is formedintegrally with said front cover, said stay having a support portion tosupport both sides of said control board, and said support portionhaving a resilient tongue with a dowel at an end thereof to be fitted ina hole provided in said control board.
 11. A casing structure for anumerical control unit, comprising:a casing body; a front cover to closea front opening of said casing body; a fan cover to be attached to a topof said front cover; a control board detachably attached to said frontcover; a guide rail provided inside said casing to guide said controlboard during insertion and to fix said control board; locking membershaving release mechanisms provided at fitting portions of said coversand said casing body; a connection board provided on a rear side of saidcasing body and connected with a terminal on said control board; acooling fan mounted on said fan cover; a terminal fixed to said fancover and connected with wiring of said cooling fan; and a power supplyterminal fixed to an upper end portion of said control board attachedupright to said front cover, to be directly connected with said terminalfixed to said fan cover; and wherein said front cover comprises a maincover and a sub-cover, and said power supply terminal to be connectedwith said terminal on said fan cover is fixed to said control boardattached to said main cover.
 12. A casing structure for a numericalcontrol unit according to claim 11, wherein said front cover and saidsub-cover are formed of synthetic resin and stays to attach and detachsaid control board are respectively formed integrally with said frontcover and said sub-cover, each of said stays having a support portion tosupport both sides of said control board, and said support portionhaving a resilient tongue with a dowel at an end thereof to be fitted ina hole provided in said control board.
 13. A casing structure for anumerical control unit, comprising:a casing body; a front cover to closea front opening of said casing body; a fan cover to be attached to a topof said front cover; a control board detachably attached to said frontcover; a guide rail provided inside said casing to guide said controlboard during insertion and to fix said control board; locking membershaving release mechanisms provided at fitting portions of said coversand said casing body; a connection board provided on a rear side of saidcasing body and connected with a terminal on said control board; acooling fan mounted on said fan cover; a terminal fixed to said fancover and connected with wiring of said cooling fan; and a power supplyterminal fixed to an upper portion of said control board attachedupright to said front cover, to be directly connected with said terminalfixed to said fan cover, wherein said front cover comprises a main coverand a sub-cover, and said casing structure further comprises a lockmechanism provided between said fan cover and said control boardattached to said main cover or between said fan cover and said maincover, to allow said main cover and said control board to be attached ordetached only when said fan cover is detached.